The present invention relates to color television receivers, and more particularly to a color television receiver adapted to receive a television signal which contains a vertical interval reference (VIR) signal for automatic correction of hue and color saturation wherein the VIR signal is disabled when the receiver is tuned to such a program source as disclosed in U.S. Pat. No. 4,178,606 granted to A. Hirota, which reproduces a recorded video signal by mixing adjacent horizontal line signals for eliminating crosstalk occurring in low-frequency color carrier signals.
Since a transmitted color television signal undergoes a phase distortion due to the inherent differential phase characteristic of the transmission path, the reproduced image tends to change in hue and color saturation from the original. The VIR signal is inserted prior to transmission into the 19th horizontal synchronization pulse position during each vertical blanking interval of the NTSC color television signal as specified by the Federal Communications Commission so as to permit receivers to automatically correct errors in hue and color saturation. The color television receiver currently includes a counter for counting the horizontal synchronization pulses during each vertical blanking interval to generate a gating pulse at the 19th count to gate on the received signal to extract the VIR signal contained therein. Therefore, there is no likelihood of the receiver erroneously discriminating it from any other signals which may be present in adjacent horizontal pulse positions.
In the current one-half inch video cassette tape recorder the azimuth angles of the recording heads are so skewed relative to each other that the horizontal line signals of each successive field signal are recorded in a direction angularly displaced from the direction in which the horizontal line signals of the adjacent field is recorded. This permits elimination of guardbands which are usually required in other video tape recorders to ensure against crosstalk between adjacent field signals. However, in the stage of reproduction this angular displacement has lesser effect of crosstalk suppression on lower frequency color carrier signals than on higher frequency signals. The current practice is to employ a one horizontal line delay circuit and a mixing circuit for mixing the input and output signals of the delay circuit for suppressing the crosstalk and so the result is an output which is an average value of the combined adjacent horizontal line signals. If the VIR inserted NTSC signal is recorded and reproduced later for application to the conventional NTSC color television receiver having the VIR correction feature, the gated VIR signal is considerably reduced in level due to the averaging effect causing an error in color saturation. The problem would become severe if other signals such as vertical interval test (VIT) signal are present in the 18th and 20th horizontal pulse positions since the averaging effect of the mixing circuit produces an output which is remarkably different from the original VIR signal, thus resulting in a totally different hue and color saturation from the original.